Method of reducing the amount of free formaldehyde in sensitized fabric for postcure durable press processing

ABSTRACT

Sensitized cotton fabrics, intended for postcure durable press processing, were subjected to aeration with moist air (10 percent to 100 percent relative humidity) or with steam for periods of time varying from about 15 seconds to 24 hours to reduce free formaldehyde content and to reduce the release of formaldehyde from the sensitized fabrics. This method does not adversely affect the use of the sensitized fabric in postcure durable press processing nor does it impair the utility, esthetics, value, or durability of the resulting durable press products.

METHOD OF REDUCING THE AMOUNT OF FREE FORMALDEHYDE IN SENSITIZED FABRIC FOR POSTCURE DURABLE PRESS PROCESSING A nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

FIELD TO WHICH INVENTION RELATES This invention relates to a method of reducing the amount of free formaldehyde on sensitized fabrics for postcure durable press processing. Specifically, this invention relates to a method wherein sensitized fabrics are aerated with moistair or steam which carries away the free formaldehyde and thereby reduces the objectionable odor associated with the formaldehyde.

DEFINITIONS By sensitized fabric we mean the use of the term as employed in the textile-finishing and garment fabrication industries. A sensitized fabric is (1) one that has been impregnated with a finishing agent, usually a methylol-amide-type crosslinking agent, capable of producing durable press properties in cotton or cellulose-containing fabrics, an agent capable of catalyzing the reaction between the finishing agent and the textile material, and (2) has been dried under conditions that do not cause any appreciable reaction between the finishing agent and the textile material. The sensitized fabric is then ready for use in the postcure durable press process. The sensitized fabric is packaged and may be stored for prolonged periods before garment manufacture in which it is cut to 'pattern, sewn, trimmed, then shaped by. pressing to introduce creases, pleats, etc., and to smooth the garment in its final configuration. The sensitized fabric in the form of a shaped garment is then cured, usually in an oven, to effect reaction of the finishing agent and the textile-material of the garment to make the shape or configuration durable to wearing and laundering. i

Postcure processing refers to that class of finishing treatments which impart durable press properties to the textile product through a postponed cure of the sensitized cloth after the textile product has been made up into a garment or other apparel or household item. The term is widely'used in the textile industry; however, the terms deferred cure or delayed cure also have been applied to this type of durable press process.

Free formaldehyde is the formaldehyde that is unreacted and is therefore free to volatilize from the sensitized fabric. The release of free formaldehyde can cause objectionable response, i.e., lachrymatory and sometimes allergenic, from those who come into proximity of the material.

THE PROBLEM In the manufacture of postcure durable press garments a serious problem is the odor of formaldehyde from sensitized fabric which cause discomfort and sometimes is an actual health hazard to those who cut, sew, and press the garments. When the packages of sensitized fabric are opened at the garment-cutting plant, the free formaldehyde is slowly released to create unpleasant and potentially unsafe working conditions. The free formaldehyde is due to (a) residual or unreacted formaldehyde which was present in the finishing solution when it was dried on the fabric or (b) to formaldehyde which has been produced due to a demethylolation of the methylolated amide compound used in finishing. The release of formaldehyde has restricted postcure finishing mainly to one agent, dimethylol dihydroxyethyleneurea (DMDHEU), which yields a sensitized fabric with moderate free formaldehyde and is relatively stable. Finishers would like, however, to reduce the formaldehyde release of fabrics sensitized with this agent, and to use other agents which are more suitable, cheaper, or have other desirable .qualities but which at present are unusable because offormaldehyde release problems.

sion of the carbamate to the dimethylol derivative.

THE PRlOR ART In the prior art means have been proposed for reducing the free formaldehyde of finishing agents. For example, it has been shown by Frick and Reinhardt, American Dyestuff Re- .porter, volume 56, No. 9,-page 41, Apr. 24, 1967, that by using lower molar ratios of formaldehyde to carbamate, an agent can be prepared which releases less formaldehyde fumes in durable press processingpHowever, this improvement is achieved at the expense-of lower level of chlorine resistance in the finished fabric.

Another approach to decreased free formaldehyde has been treatment of the solution of methylolated finishing agent with a chemical reactant which combines with the free formaldehyde and thusbinds it from release during fabric processing. Although successful in controlling free formaldehyde, undesireable collateral effects on the finished fabric have been produced by this chemical technique. principally decreased durability and decreased chlorine resistance of the finish upon hydrolysis and severe laundering. Chemical methods of this type have been disclosed by Reid, Kullman, and Reinhardt (Proceedings of the Ninth Cotton Utilization Research Conference, Apr. 30-May 2, 1969, New Orleans, Louisiana).

OBJECT OF THE INVENTION It is an object of the instant invention to provide new methods for decreasing the free formaldehyde of sensitized fabricused in postcure finishing without adverse effect on the processing and without inducing undesirable side effects that impair the.utility;esthetics, value, or durability of the resulting durable press products.

HOW THE OBJECTS ARE ACHIEVED The objectives are achieved by methods in which the sensitized fabrics are aerated by subjecting them to moist air or steam which releases and carries away the free formaldehyde. Aeration thus reduces the free formaldehyde of the fabric without the necessity (l) of any change in thepreparation of the finishing agent, (2) of additional reaction of the finishing agent solution with other chemical agents, or (3) of any other modification of the conventional postcure durable press process. Because of the absence of such changes and modifi cations, aeration accomplishes the objective of decreased free formaldehyde without effect on the desirable characteristics of the finish andwithout introducing additional undesirable characteristics.

Our investigations have revealed that free formaldehyde is tenaciously held by sensitized cellulosic materials if the fabric is dry. We have found that the formaldehyde will be released from the sensitized fabricby aeration, that is, by treatment with large volumes of air, provided that sufficient moisture is present, or with steam. Therefore, free formaldehydeis conveniently removed by a process of blowing moist air or steam onto or through the fabric. The amount of moisture present in the air employed for aeration may be varied from about that necessary to givea level of relative humidity of about 10 percent up to that of a moisture-saturated atmosphere percent relative humidity). The efficacy of aeration, however, is a function of'the amount of moisture present in the air. Thus. higher levels of moisture in the air employed in aeration are preferred to affect more rapid and more completereduction in the amount of free formaldehyde of the sensitized fabric.

United States Patent John D. Reid New Orleans;

Robert M. Reinhardt, New Orleans; Russell M. H. Kullman, Metairie, all of La. 884,706

Dec. 12, 1969 Nov. 2, 1971 The United States of America as represented by the Secretary of Agriculture Inventors Appl. No. Filed Patented Assignee METHOD OF REDUCING THE AMOUNT OF FREE FORMALDEIIYDE IN SENSITIZED FABRIC FOR POSTCURE DURABLE PRESS PROCESSING 3 Claims, No Drawings U.S. Cl 8/1l6.3, 38/144, 2/243,1l7/139.4

Int. Cl 006m 13/12, D06m 13/34 Field of Search 8/1 16.3; 38/144 References Cited OTHER REFERENCES Reid et al., American Dyestuff Reporter, Vol. 59, No. 6, pp. 26- 28, 32 and 34 1970) Primary ExaminerGeorge F. Lesmes Assistant Examiner.l. Cannon Attorneys-R. Hoffman and W. Bier method does not adversely affect the use of the sensitized fabric in postcure durable press processing nor does it impair the utility, esthetics, value, or durability of the resulting durable press products.

Molar Ratio Sensitized sensitized-Aerated 2.2 0.67 0.12 3.0 LIZ 0.16

Example 4 Treating solutions were prepared from solutions of the dimethylol derivatives of hydroxyethyl carbamate, methoxyethyl carbamate, ethyleneurea, and dihydroxyethyleneurea. Each treating solution also contained 0.6 percent zinc nitrate hexahydrate.

Three swatches of cotton cloth were impregnated with each treating solution by passing into and through the solution squeezing and repeating the process. One portion (wet) was immediately analyzed for free formaldehyde content, the other portions were sensitized by drying at 60 C. for 7 minutes. Immediately after drying, one sensitized portion was analyzed for free formaldehyde content. The remaining portion was aerated in ambient moist air for 24 hours and then analyzed for free formaldehyde content. The results shown in table lV clearly illustrates the obvious advantage of aeration. It is further obvious that the aeration method for decreasing free formaldehyde is applicable to sensitized fabrics treated with a variety of methylolated finishing agents. Thus many agents whose use in postcure processing has been inhibited due to objectionable formaldehyde release may be satisfactory if aeration is included in the processing sequence.

Cotton fabric was sensitized with dimethylol methyl carbamate as in example I. Portions were hung in a chamber and aerated by blowing air past the surface of the sensitized fabric. Moist air (65 percent relative humidity), moisture-saturated air, and dry air were investigated. Periodically portions of fabric were removed and analyzed for free formaldehyde content. Table V illustrates the effectiveness of moisture in air as well as the dynamic effect of causing air to flow past the fabric during aeration. Time to reduce free formaldehyde content in sensitized fabric is greatly accelerated by this technique.

TABLE V Free Formaldehyde in Fabric After Dynamic Aeration with Aeration Time Moisture- Moist Air Hours Saturated Air (65% RH) Dry Air 0 (sensitized) 0.18 0.18 0.18

Example 6 Cotton fabric was sensitized with dimethylol methyl carbamate as in example 1. Portions of the sensitized fabric were placed in a chamber and aerated in a manner such that air was passed through the fabric. Moisture in the air was controlled as in example 5. Results in table VI demonstrate the effectiveness of dynamic flow of moist air through the sensitized fabric to reduce free formaldehyde content.

TABLE VI Free Formaldehyde in Fabric After Dynamic Aeration with A cotton cloth was passed into and through a solution containing 10 percent formaldehyde and 0.6 percent zinc nitrate hexahydrate, squeezed, and the process repeated. The wet fabric was sensitized by drying at 60 C. for 7 minutes. A portion (sample A) of the sensitized fabric was immediately analyzed for free formaldehyde content (%FF): three sensitized portions (samples B, C, D) were aerated by hanging in ambient laboratory air (70 percent RH, 24 C.); three sensitized portions (samples E, F, 0) were steamed and redried, and three sensitized portions (samples H, l, 1) were aerated as samples B, C, D but then redried as samples H, l, J. To accomplish aeration by steaming, fabric was hung for 30 seconds in a cylindrical flue with steam passing through, then the fabric was removed and dried 3 minutes at 60 C. Sample E, after steaming and drying, was immediately analyzed for free formaldehyde, the process of steaming and drying was repeated again for sample F and twice more for sample G before each was analyzed. Sample H was redried with sample E then samples B, E, and H were analyzed concurrently. In this manner, samples B, C, D served as aerated controls and samples H, l, J served as aerated, redried controls for samples E, F, or G, respectively. Thus the longest elapsed time between sensitizing and analysis was about 15 minutes. Aeration with ambient room air for this short period is not sufficient to substantially reduce free formaldehyde although steaming effected substantial reductions in free formaldehyde as shown in table Vll.

The results clearly illustrate that removal of free formaldehyde is greatly accelerated by use of steam and that oven heat alone, that is, redrying, is not sufficient to accomplish the same reduction of free formaldehyde in sensitized fabric.

Example 8 A cotton cloth was passed into and through a solution containing 10 percent dimethylol methyl carbamate and 0.6 percent zinc nitrate hexahydrate, squeezed, and the process repeated. The wet fabric was sensitized by drying at 60 C. for 7 minutes. One portion was immediately analyzed for free formaldehyde three portions were used as aerated controls and three portions were steamed and redried as in example 7. The results on table VIII provide further evidence that steaming of sensitized fabrics rapidly decreases free formaldehyde. Repeating the steaming cycle can completely eliminate the free formaldehyde.

.TABLE VIII No. Free Formaldehyde, Steamings- Redryings Steam-redried Aerated control Example 9 A cotton cloth was sensitized as in example 8. One portion was immediately analyzed for free formaldehyde, other portions were steamed for various times, redried, and then analyzed. As seen in table IX, the decrease of free formaldchyde in sensitized fabric is a function of time of steaming. Complete elimination of free formaldehyde was achieved upon steaming for between 1 and 2 minutes.

TABLE IX Steaming time, Free Formaldehyde.

minutes We claim:

1. A method of lowering formaldehyde exudation from a cellulosic fabric which has been sensitized through treatment with a methylolated nitrogen containing cellulose cross-linking agent to the degree that it is capable of being subsequently cured to produce durable press products comprising aerating the sensitized fabric by passing moist air at ambient temperature thereon or therethrough for a period of about 30 minutes to 24 hours to reduce the formaldehyde content thereof without desensitizing the fabric.

2. A method of lowering formaldehyde exudation from a cellulosic fabric which has been sensitized through treatment with a methylolated nitrogen containing cellulose cross-linking agent to the degree that it is capable of being subsequently cured to produce durable press products comprising aerating the sensitized fabric by passing steam thereon or therethrough for a period of about 15 seconds to 4 minutes to reduce the formaldehyde content thereof without desensitizing the fabric. 3. A method of lowering formaldehyde exudation from a cellulosic fabric which has been sensitized through treatment with a methylolated nitrogen containing cellulose cross-linking agent to the degree that it is capable of being subsequently cured to produce durable press products comprising aerating the sensitized fabric by alternately steaming said fabric for a period of about 30 seconds and drying said fabric to reduce the formaldehyde content thereof without desensitizing the fabric. 

2. A method of lowering formaldehyde exudation from a cellulosic fabric which has been sensitized through treatment with a methylolated nitrogen containing cellulose cross-linking agent to the degree that it is capable of being subsequently cured to produce durable press products comprising aerating the sensitized fabric by passing steam thereon or therethrough for a period of about 15 seconds to 4 minutes to reduce the formaldehyde content thereof without desensitizing the fabric.
 3. A method of lowering formaldehyde exudation from a cellulosic fabric which has been sensitized through treatment with a methylolated nitrogen containing cellulose cross-linking agent to the degree that it is capable of being subsequently cured to produce durable press products comprising aerating the sensitized fabric by alternately steaming said fabric for a period of about 30 seconds and drying said fabric to reduce the formaldehyde content thereof without desensitizing the fabric. 